1. Field of the Invention
The present invention relates to a collision warning device for motor vehicles, having a locating system for locating objects in the area in front of the vehicle and a control device for evaluating the data of the locating system and for outputting a warning signal in the event of an imminent risk of a collision, and having a detection module for detecting the course of guardrails with the aid of data from the locating system.
2. Description of Related Art
Such collision warning devices are to help the driver guide the motor vehicle and help reduce the risk of an accident and/or help lessen the consequences of an accident, and are also known as PSS systems (predictive safety systems). The locating system is usually formed by a radar sensor allowing angular resolution, with which the distances, relative speeds, and azimuth angles of the located objects can be measured. With the aid of these data and with the aid of the dynamic data of the vehicle, the control device then calculates a so-called “time to collision,” that is, the time after which the collision would occur if the dynamic state of the vehicle does not change. If this time lies below a specific threshold value, the warning signal is output, which may then be converted into an acoustic warning for the driver, for example, in order to alert the driver to the imminent risk. Furthermore, with the aid of the warning signal, some PSS systems are also able to trigger automatically suitable countermeasures, for example, an emergency braking, in order to avert the collision or at least to lessen its consequences.
Furthermore, so-called ACC systems (adaptive cruise control) are known, with which the vehicle's distance from a preceding vehicle located by the radar sensor may be regulated automatically. Within the framework of this regulation, only vehicle accelerations and decelerations that are within certain limits that are still perceived as comfortable for the vehicle occupants are permitted. When the traffic situation calls for a stronger vehicle deceleration, these systems also output a warning signal, which is to cause the driver to take control himself. In this respect, an ACC system may also be considered to be a collision warning device in the sense of the present invention.
While traditional PSS and ACC systems only react to moving objects, that is, in particular to preceding vehicles, efforts are made to include stationary objects in the evaluation as well, so that a collision warning may also be output when the host vehicle is approaching a stationary vehicle forming the end of a traffic jam, for example. However, the evaluation of stationary objects requires a significantly higher data processing effort, since the number of objects to be considered is then significantly greater and apart from this in many cases it is difficult to make a decision regarding whether a located object is a real obstacle or only an irrelevant object, such as a traffic sign on the side of the road or the like.
Published International PCT patent document WO 2006/128766 describes a collision warning device, which is able to use characteristic patterns to detect specific object classes in the data supplied by the locating system, even guardrails, among other things. The information about the guardrails may then be used to plausibilize the anticipated travel corridor of the host vehicle, so that a decision may be made more reliably regarding whether a located stationary object is a real obstacle on the road, or whether the object is located beyond the guardrail on the side of the road.
Furthermore, so-called lane-maintenance assistants or lane-departure warning systems are known, which use a video system to detect the course of the sides of the road and trigger a warning signal or an automatic steering intervention when the driver is about to leave the lane in which he is currently driving.